The principle purpose of the project is to understand better the mechanism of DNA synthesis in normal and neoplastic cells. Current projects are primarily in two areas: 2. Clarification of the mechanism of initiation of new chains, specifically evidence on RNA priming. 2. Development of new systems for the study of DNA synthesis, in vitro; particularly utilizing parvovirus H-l-infected HeLa cells; to identify components of the replication apparatus and their mechanism of action. BIBLIOGRAPHIC REFERENCES: Mendelsohn, J., Fox, R., Goulian, M. and Barbosa, D.: Nascent DNA from phytohemagglutinin-stimulated lymphocytes. Immun. Comm. 4:373, 1975. Mendelsohn, J., Castagnola, J.M. and Goulian, M.: On the mechanism for formation of RNA-DNA complexes from lymphocytes. Biochem. Biophys. Acta 407:283, 1975.